Biology; Chemistry; Physics: Post your doubts here!

[Dashing Cancerian]

At the start of the journey , there is opposite air resistance and frictional force of 3200 N which causes the truck to move at an acceleration of 3.52 m/s^2 with a resultant force of 8800 N (12000-3200) in the forward direction. As it speeds up , the counter forces (Air resistance and Friction which reduces its acceleration) also increase at the same rate until the resultant force acting on the truck is zero and the then car moves at constant speed.

For example : At the start journey its acceleration was 3.52m/s^2 . After a time of 20 seconds the opposite force acting on the truck is 6000 N so by using F=ma formula ( where F= 12000-6000=6000N , m=2500) acceleration will be 2.4 m/s^2 and this shows that its acceleration has been reduced . And later on when resultant force = 0 , acceleration would be zero and the truck will move at constant speed.

I hope you get it though Im not sure if its right or not

but there is no proportion of forward force to counter forces until the truck is climbing a hill or mountain... it doesnt matter that if the forward force is increasing or not, I guess there is a problem with ur answer there nd i knw hw to find acceleration but couldnt get how the truck will decelerate and then come back to constant speed.

 

[ashfaaq7]

Test for iodine ion and its result.......<reply immediately>

 

[Most_UniQue]

but there is no proportion of forward force to counter forces until the truck is climbing a hill or mountain... it doesnt matter that if the forward force is increasing or not, I guess there is a problem with ur answer there nd i knw hw to find acceleration but couldnt get how the truck will decelerate and then come back to constant speed.

Forward force remains constant. What I said was that as speed increases , the counter forces also increase which reduce its acceleration. Speed is constant when resultant force and acceleration is zero .

 

[Most_UniQue]

Also F is proportional to acceleration so when resultant force is reduced , acceleration reduces also.

 

[scouserlfc]

all non metals make acidic oxides such as co2..so oxygen probably is too!

If u guys are talking abt oxygen if its acidic or basic its slightly basic while CO2 is acidic !

 

[Alchemist4lyf]

Forward force remains constant. What I said was that as speed increases , the counter forces also increase which reduce its acceleration. Speed is constant when resultant force and acceleration is zero .

I really don't think this question has to be answered quantitatively. You see, we found out the body is accelerating. And that acceleration, is 3.52. Now, that is a positive acceleration, which is increasing the velocity of the body as it is greater than 1. Now, as we might recall, friction is a force that increases with the speed of the body. The same goes for any other type of opposing force, such as air resistance. The body is increasing its velocity, so the opposing force also increases. Then, it reaches a point when it is equal to the body's speed, thereby not allowing further acceleration. That is why a constant velocity is reacher.
Bear in mind, opposing forces such as friction and air resistance are NEVER greater than the force provided by the body. They have different values DEPENDING on the provided force. I don't think there's much difference between this question, and the concept of terminal velocity.
You are correct on this question, I don't get what's more to it? :/

 

[Alchemist4lyf]

Oh, and I have a small question. How is it, that the speed of sound is affected by temperature and humidity changes? I have a slight idea, but I'm not really sure about it. Can you help a brother out?

 

[Dashing Cancerian]

Forward force remains constant. What I said was that as speed increases , the counter forces also increase which reduce its acceleration. Speed is constant when resultant force and acceleration is zero .

i got it... thnx....

 

[Most_UniQue]

Oh, and I have a small question. How is it, that the speed of sound is affected by temperature and humidity changes? I have a slight idea, but I'm not really sure about it. Can you help a brother out?

Dude at higher temperatures , particles of air vibrate faster and thus allows sound waves to travel faster too.

According to the formula v= 331 m/s + 0.6 m/s / C*T , it states that for a rise of 1*C , the speed of sound increases by 0.6 m/s.

As for humidity , the air is more dense when its more humid . Sound travels faster through denser medium then a rare one because the particles of air are close together so they vibrate at faster rate due to collision which produces more energy for the particles to vibrate .

Hope you get it Im not so sure about the humidity one...

 

[Alchemist4lyf]

Thanks a lot mate. I was thinking the answer was something along those lines, but that formula thingy, helped.

 

[Sweetsilly]

Can someone kindly provide me with the notes of

1. Distillation
2. Fractional Distillation
3. Chromatography

 

[mmn1995]

yar i need merchant chem n bio notes.need physics naushad notes too.pls help someone!

 

[Most_UniQue]

Thanks a lot mate. I was thinking the answer was something along those lines, but that formula thingy, helped.

Your welcome

 

[Most_UniQue]

Can someone kindly provide me with the notes of

1. Distillation
2. Fractional Distillation
3. Chromatography

Here mate... If you still dont get it , I got more notes....

 

[sweetiepie]

Can someone kindly provide me with the notes of

1. Distillation
2. Fractional Distillation
3. Chromatography

http://www.xtremepapers.com/communi...ry-physics-post-your-doubts-here.9672/page-11 check here last post on page

 

[aleezay]

biology help needed-have a look at Q2

 

[aleezay]

Also,can anyone help me out in phy? Papers:
5040_w11_qp22 Q7b(ii)
5040_w11_qp21 Q9b(v)
sorry i cudnt upload the papers..

 

[scouserlfc]

biology help needed-have a look at Q2

Whats the problem with Ques 2 its a normal sketching question !

 

[ashfaaq7]

Can someone kindly provide me with the notes of

1. Distillation
2. Fractional Distillation
3. Chromatography

Simple Distillation
Simple Distillation – separation of pure liquid from a solution by condensing vaporised liquid
Condensed pure liquid – distillate
Process of Distillation:
Solution is heated, and steam (pure vapour) is produced. The steam is cooled in condenser to form pure liquid. Solute remains in the flask.
Fractional Distillation
Fractional Distillation – separates mixture of miscible (soluble) liquids with widely differing boiling points.
Use of fractionationg column separates them
Process of Fractional Distillation: E.g. ethanol and water
Mixture of ethanol and water is placed in flask and heated. Ethanol with lower boiling point boils and vaporises first and reach fractionating column then cools and condenses into ethanol as it passes through condenser. Temperature will stay constant until all ethanol is distilled. Water will distil the same way after all ethanol is distilled.
Diagram and Distillation Graph
Uses of fractional distillation:
- Separates pure oxygen and pure nitrogen from liquefied air
- Separates substances in petroleum (crude oil) into fractions
- Separates alcohol to produce alcoholic drinks
Reverse Osmosis
Reverse Osmosis – separates a solution (e.g. seawater) by pressurizing the mixture against a membrane which separates the solute and the solvent
Seawater is pumped under great pressure into a closed container onto a membrane forcing water particles but salt particles to pass through. Some salt particles may still pass through.

Chromatography

Separating Mixtures of Coloured Substances
Obtain a dye sample then put a drop of the sample on a pencil line drawn on the filter paper then dip the paper into a solvent with the level below the spot. The dye will dissolve in solvent and travel up the paper at different speed. Hence they are separated.
Identifying Mixturees of Coloured Substances
In the diagram on the right, drop of sample dye is placed on pencil line. The result shows that:
- The sample dye is made of 3 colours.
- 2 comparison dyes are of one of the compositions of the original dye as the spots are of same colour and distance.
- a comparison dye isn’t part of sample.
Separating and Identifying Mixtures of Colourless Substances
To do this a locating agent is to be sprayed on filter paper.
Locating Agent – a substance that reacts with substances (e.g. sugars) on paper to procuce a coloured product.
Rf Values
To identify unknown dye in the diagram at the very top:
Rf value =
Where x = distance moved by the substance and;
y = distance moved by the solvent
Checking the Purity of Substances
- Pure substances have FIXED MELTING AND BOILING POINTS.
 Pure water boils at 100oC and melts at 0oC.
- Impure substances have NO FIXED MELTING AND BOILING POINTS. They melt and boil at a RANGE OF TEMPERATURES
 e.g. starts boil at 70oC, completes boil at 78oC
 Also, it can VARY melting and boiling points of pure substances.
 e.g. pure water boil at 100oC, but with salt is at 102oC

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[asadasad]

2

Re: Biology,Chemistry & Physics Help Available Here !

Here is my question:
If a mass-less box travels at 7.293 x 10^0 microdoodles, what time will it be in Karachi when Altaf Hussain next sings the song 'Parday main rehney doh'?

2022